Looking at a mismatched set of ULH cases on Ebay ... Serial number looks very good to my eye, but I was surprised to see that the bottom number on the left side was an exact match. Obviously, this is possible, but just wondered if that would bother anybody ... The bottom number looks pretty good to me as well.

Not really answering your question, not enough knowledge on the subject to help anyway. Just wanted to say I bought from this seller 2 or 3 times in the past and his parts were perfect and he's a great guy to deal with.

I think it's possible that X-WLCH was speaking in generalizations. As long as the serial number is good/authentic I don't worry too much about belly numbers. My '37 has absolutly good serial numbers, but the the belly #'s are matching 1941 numbers. Those old engines have been through a lot of use and abuse and it makes sense that there are more miss matched numbers out there than matching.

if you look at a lot of numbers you will notice that the belly numbers and the serial number are within 200 of each other, This certainly isn't always the case , and i wouldn't have any concerns if my numbers were not within 200 of each other, but about 80% of the time they are. As I recall ( from this forum ) is was speculated that each engine assembler worked on lots of 200 engines at a time. I don't have any personal knowledge of this but it dose seem to work out. There are others on this forum that do have old company information and may be able to share some more info on this.

X-WLCH, thanks for the reply. I‘ve heard before about the relationship between SNs and BNs and I began recording examples of many years and models a while back. I checked my photo collection for 1937–48 U-series SNs that I also have BNs for and I found 93 examples which appear to be factory-stamped, excluding the example at the start of this thread. The only model year not represented is 1943. Examples within 200 of each other: 55.Examples more than 200 apart from each other: 33. (Of the 33, seven are close enough, being no more than 221 apart from each other.)Because in some instances some characters were hidden by the owners, five examples could go either way and it’s possible as many as three of that five could result in matching numbers although of course it isn’t very likely that any would.

It’s also interesting to note that on 50 occasions the SN was higher than the BN and 39 times it was lower. In four instances it could go either way, again due to some characters being hidden by the owners. Eric

knucklebolt wrote:As long as the serial number is good/authentic I don't worry too much about belly numbers. My '37 has absolutly good serial numbers, but the the belly #'s are matching 1941 numbers. Those old engines have been through a lot of use and abuse and it makes sense that there are more miss matched numbers out there than matching.

Did that make sense?

ken

Ken, you said it makes sense that there are more mismatched numbers out there than matching. But I think you may have missed the point? We weren’t talking about BNs matching each other or not; instead we were talking about the sequence portion of the BN matching the sequence portion of the accompanying SN.

You also said your '37 has an absolutely good SN but the BNs are matching 1941. And I’m assuming you mean a Big Twin Flathead? But what exactly are you calling an absolutely good SN? Your SN isn’t factory-stamped is it? It sounds like you have a 37 SN on replacement cases with 41 BNs? And if so was the SN applied by a Harley dealer? In other words, given that for 1937 the models available were the U, UH, UHS, UL, ULH and US, how do you know the SN sequence portion is the one originally assigned at the factory to the model you have?Eric

Yes Eric I did miss the point a bit. I was just saying that I wouldn't be worried about SN's matching the BN's as long as the SN looked clean and authentic, but no that wasn't the point. !!

I have had some experience with stolen bikes/altered SN's, and I was just saying that I'm convinced the SN's on my big twin 74 are real, really an almost "textbook" example of good numbers and a unmolested SN boss, but I wouldn't have any idea if they were stamped on replacement cases at the factory, stamped at a dealer, or just how the cases were replaced and stamped. So no, I don't know, and yes I did miss the point. !!

Speeding Big Twin wrote:X-WLCH, thanks for the reply. I‘ve heard before about the relationship between SNs and BNs and I began recording examples of many years and models a while back. I checked my photo collection for 1937–48 U-series SNs that I also have BNs for and I found 93 examples which appear to be factory-stamped, excluding the example at the start of this thread. The only model year not represented is 1943. Examples within 200 of each other: 55.Examples more than 200 apart from each other: 33. (Of the 33, seven are close enough, being no more than 221 apart from each other.)Because in some instances some characters were hidden by the owners, five examples could go either way and it’s possible as many as three of that five could result in matching numbers although of course it isn’t very likely that any would.

It’s also interesting to note that on 50 occasions the SN was higher than the BN and 39 times it was lower. In four instances it could go either way, again due to some characters being hidden by the owners. Eric

Hi DonDo you know how Mr. Andres marked the line bore numbers on replacement cases, and was there a HD policy ? Can it be assumed that the replacement case got the same serial number as the original ? Jim.

X-WLCH wrote:Hi DonDo you know how Mr. Andres marked the line bore numbers on replacement cases, and was there a HD policy ? Can it be assumed that the replacement case got the same serial number as the original ? Jim.

"to correct myself.Can it be assumed that the replacement case got the same "line bore" number as the original ?"jim. Jim,1st Q NO. Line bore #'s Done at factory at line boring for that Year's production plus spares sold to dealers, 2nd Q Yes.,3rd Q No. Maybe if some dealer had pull with the factory.

Side note; Leonard had enough pull to have the factory racing team use one of his motors at Daytona. (This from several people who raced his bikes So. Cal.)Seeing an impending loss, a phone call was made, his engine was used, they won.

knucklebolt wrote:Yes Eric I did miss the point a bit. I was just saying that I wouldn't be worried about SN's matching the BN's as long as the SN looked clean and authentic, but no that wasn't the point. !!

I have had some experience with stolen bikes/altered SN's, and I was just saying that I'm convinced the SN's on my big twin 74 are real, really an almost "textbook" example of good numbers and a unmolested SN boss, but I wouldn't have any idea if they were stamped on replacement cases at the factory, stamped at a dealer, or just how the cases were replaced and stamped. So no, I don't know, and yes I did miss the point. !!

ken.

Ken, thanks for the response and I hope you didn’t take offence. I agree it isn’t a worry for the SN to match the BNs as long as everything looks authentic.

Good to hear the number boss on your BT 74 is unmolested but I don’t know how you’re convinced the SN is real if you have no idea who stamped it, and given the different model possibilities I mentioned above. Because you said your SN is an almost "textbook" example of good numbers will I assume you mean it consists of characters used by the factory for 1937 models? If so then there’s the question of whether said characters were early-37 H-D styles or later-37 H-D styles, along with the possibility of exceptions to that apparent early vs later rule.

If your SN is almost textbook to the point that all characters appear to be either early-37 H-D or later-37 H-D depending on SN, then I’d say there’s a fair chance it was applied on replacement 1941 cases by Harley, either at a dealership or at the factory. Eric

I have photos of cases that appear to be replacements and some have two or three numbers in the BN area as per the Knucklehead set below with 43. Both these halves were cast in December 1947. Because 43 is in the centre of the usual BN location it would seem it wasn’t meant to be part of the normal format of a Knuckle BN and may instead have just been a way of identifying them as a matched pair. And as you can see, the number boss is unstamped and appears unaltered.

A separate and lone Knuckle left case, again of later-41-–47 style, has 105 stamped in the same position as the cases with 43 on them. Its number boss appears unstamped and unaltered.Another lone Knuckle left case has 15 stamped in the same position as the 43 and 105. Number boss is unstamped and appears unaltered. A set of V-series cases have 42 in that same central area of the normal BN position. Number boss is unstamped and appears unaltered.

Some other photos I have of cases that appear to be replacements show the usual style of BNs fully formatted and they look factory-stamped. Number bosses unstamped and unaltered. Eric

I bought the 47ULxxxxx with 43-2232 * B 1 * on Cebu Island P.I. early '70s 47 and 5 numerals Larger than Factory numbers, ul is Lower case, half size of #'s. Origin was USNavy base Cebu city (motor pool) or J.A.N. airbase Mactan. There were later OHV models running around the city.

Thanks, Don. That’s certainly unusual having ul in lower case. I have plenty of non-factory examples in my photo collection but at the moment I can't recall one having lower-case letters.

I don’t know exactly what 43 in my photo relates to. Both halves were cast in December 1947 and I’m assuming at this stage that 43 only identifies the cases as a matched pair and nothing more. And I think the same may be true for the other examples I have such as the case with 105. It was cast in January 1948 but it seems to be just a regular left half and I posted it below:

No date code on your 38 case with the numbers you provided is consistent with my findings thus far. On a crankcase the earliest letter-number date code I’ve seen is C 8 and the BN is 38-3247 (Knuckle R-H case).Eric